﻿// Copyright � 2004, 2014, Oracle and/or its affiliates. All rights reserved.
//
// MySQL Connector/NET is licensed under the terms of the GPLv2
// <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most 
// MySQL Connectors. There are special exceptions to the terms and 
// conditions of the GPLv2 as it is applied to this software, see the 
// FLOSS License Exception
// <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
//
// This program is free software; you can redistribute it and/or modify 
// it under the terms of the GNU General Public License as published 
// by the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful, but 
// WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
// or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
// for more details.
//
// You should have received a copy of the GNU General Public License along 
// with this program; if not, write to the Free Software Foundation, Inc., 
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System.Collections.Generic;
using System;
using System.Data;
using System.Globalization;
using System.IO;
using System.Threading.Tasks;
using System.Threading;

namespace MySqlConnector
{
    /// <summary>
    /// Provides a class capable of executing a SQL script containing
    /// multiple SQL statements including CREATE PROCEDURE statements
    /// that require changing the delimiter
    /// </summary>
    public class MySqlScript
    {
        private MySqlConnection connection;
        private string query;
        private string delimiter;

        public event MySqlStatementExecutedEventHandler StatementExecuted;
        public event MySqlScriptErrorEventHandler Error;
        public event EventHandler ScriptCompleted;

        #region Constructors

        /// <summary>
        /// Initializes a new instance of the 
        /// <see cref="MySqlScript"/> class.
        /// </summary>
        public MySqlScript()
        {
            Delimiter = ";";
        }

        /// <summary>
        /// Initializes a new instance of the 
        /// <see cref="MySqlScript"/> class.
        /// </summary>
        /// <param name="connection">The connection.</param>
        public MySqlScript(MySqlConnection connection)
          : this()
        {
            this.connection = connection;
        }

        /// <summary>
        /// Initializes a new instance of the 
        /// <see cref="MySqlScript"/> class.
        /// </summary>
        /// <param name="query">The query.</param>
        public MySqlScript(string query)
          : this()
        {
            this.query = query;
        }

        /// <summary>
        /// Initializes a new instance of the 
        /// <see cref="MySqlScript"/> class.
        /// </summary>
        /// <param name="connection">The connection.</param>
        /// <param name="query">The query.</param>
        public MySqlScript(MySqlConnection connection, string query)
          : this()
        {
            this.connection = connection;
            this.query = query;
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets or sets the connection.
        /// </summary>
        /// <value>The connection.</value>
        public MySqlConnection Connection
        {
            get { return connection; }
            set { connection = value; }
        }

        /// <summary>
        /// Gets or sets the query.
        /// </summary>
        /// <value>The query.</value>
        public string Query
        {
            get { return query; }
            set { query = value; }
        }

        /// <summary>
        /// Gets or sets the delimiter.
        /// </summary>
        /// <value>The delimiter.</value>
        public string Delimiter
        {
            get { return delimiter; }
            set { delimiter = value; }
        }

        public bool AnsiQuotes { get; set; } = true;
        public bool NoBackslashEscapes { get; set; } = true;

        #endregion

        #region Public Methods

        /// <summary>
        /// Executes this instance.
        /// </summary>
        /// <returns>The number of statements executed as part of the script.</returns>
        public int Execute()
        {
            bool openedConnection = false;

            if (connection == null)
                throw new InvalidOperationException("Connection not set");
            if (query == null || query.Length == 0)
                return 0;

            // next we open up the connetion if it is not already open
            if (connection.State != ConnectionState.Open)
            {
                openedConnection = true;
                connection.Open();
            }

            // since we don't allow setting of parameters on a script we can 
            // therefore safely allow the use of user variables.  no one should be using
            // this connection while we are using it so we can temporarily tell it
            // to allow the use of user variables
            //bool allowUserVars = true;

            try
            {
                // first we break the query up into smaller queries
                List<ScriptStatement> statements = BreakIntoStatements();

                int count = 0;
                MySqlCommand cmd = new MySqlCommand(null, connection);
                foreach (ScriptStatement statement in statements)
                {
                    if (String.IsNullOrEmpty(statement.text)) continue;
                    cmd.CommandText = statement.text;
                    try
                    {
                        cmd.ExecuteNonQuery();
                        count++;
                        OnQueryExecuted(statement);
                    }
                    catch (Exception ex)
                    {
                        if (Error == null)
                            throw;
                        if (!OnScriptError(ex))
                            break;
                    }
                }
                OnScriptCompleted();
                return count;
            }
            finally
            {
                if (openedConnection)
                {
                    connection.Close();
                }
            }
        }

        #endregion

        private void OnQueryExecuted(ScriptStatement statement)
        {
            if (StatementExecuted != null)
            {
                MySqlScriptEventArgs args = new MySqlScriptEventArgs();
                args.Statement = statement;
                StatementExecuted(this, args);
            }
        }

        private void OnScriptCompleted()
        {
            ScriptCompleted?.Invoke(this, EventArgs.Empty);
        }

        private bool OnScriptError(Exception ex)
        {
            if (Error != null)
            {
                MySqlScriptErrorEventArgs args = new MySqlScriptErrorEventArgs(ex);
                Error(this, args);
                return args.Ignore;
            }
            return false;
        }

        private List<int> BreakScriptIntoLines()
        {
            List<int> lineNumbers = new List<int>();

            StringReader sr = new StringReader(query);
            string line = sr.ReadLine();
            int pos = 0;
            while (line != null)
            {
                lineNumbers.Add(pos);
                pos += line.Length;
                line = sr.ReadLine();
            }
            return lineNumbers;
        }

        private static int FindLineNumber(int position, List<int> lineNumbers)
        {
            int i = 0;
            while (i < lineNumbers.Count && position < lineNumbers[i])
                i++;
            return i;
        }

        private List<ScriptStatement> BreakIntoStatements()
        {
            string currentDelimiter = Delimiter;
            int startPos = 0;
            List<ScriptStatement> statements = new List<ScriptStatement>();
            List<int> lineNumbers = BreakScriptIntoLines();
            MySqlTokenizer tokenizer = new MySqlTokenizer(query);

            tokenizer.AnsiQuotes = AnsiQuotes;
            tokenizer.BackslashEscapes = !NoBackslashEscapes;

            string token = tokenizer.NextToken();
            while (token != null)
            {
                if (!tokenizer.Quoted)
                {
                    if (token.ToLower(CultureInfo.InvariantCulture) == "delimiter")
                    {
                        tokenizer.NextToken();
                        AdjustDelimiterEnd(tokenizer);
                        currentDelimiter = query.Substring(tokenizer.StartIndex,
                          tokenizer.StopIndex - tokenizer.StartIndex).Trim();
                        startPos = tokenizer.StopIndex;
                    }
                    else
                    {
                        // this handles the case where our tokenizer reads part of the
                        // delimiter
                        if (currentDelimiter.StartsWith(token, StringComparison.OrdinalIgnoreCase))
                        {
                            if ((tokenizer.StartIndex + currentDelimiter.Length) <= query.Length)
                            {
                                if (query.Substring(tokenizer.StartIndex, currentDelimiter.Length) == currentDelimiter)
                                {
                                    token = currentDelimiter;
                                    tokenizer.Position = tokenizer.StartIndex + currentDelimiter.Length;
                                    tokenizer.StopIndex = tokenizer.Position;
                                }
                            }
                        }

                        int delimiterPos = token.IndexOf(currentDelimiter, StringComparison.OrdinalIgnoreCase);
                        if (delimiterPos != -1)
                        {
                            int endPos = tokenizer.StopIndex - token.Length + delimiterPos;
                            if (tokenizer.StopIndex == query.Length - 1)
                                endPos++;
                            string currentQuery = query.Substring(startPos, endPos - startPos);
                            ScriptStatement statement = new ScriptStatement();
                            statement.text = currentQuery.Trim();
                            statement.line = FindLineNumber(startPos, lineNumbers);
                            statement.position = startPos - lineNumbers[statement.line];
                            statements.Add(statement);
                            startPos = endPos + currentDelimiter.Length;
                        }
                    }
                }
                token = tokenizer.NextToken();
            }

            // now clean up the last statement
            if (startPos < query.Length - 1)
            {
                string sqlLeftOver = query.Substring(startPos).Trim();
                if (!String.IsNullOrEmpty(sqlLeftOver))
                {
                    ScriptStatement statement = new ScriptStatement();
                    statement.text = sqlLeftOver;
                    statement.line = FindLineNumber(startPos, lineNumbers);
                    statement.position = startPos - lineNumbers[statement.line];
                    statements.Add(statement);
                }
            }
            return statements;
        }

        private void AdjustDelimiterEnd(MySqlTokenizer tokenizer)
        {
            if (tokenizer.StopIndex < query.Length)
            {
                int pos = tokenizer.StopIndex;
                char c = query[pos];

                while (!Char.IsWhiteSpace(c) && pos < (query.Length - 1))
                {
                    c = query[++pos];
                }
                tokenizer.StopIndex = pos;
                tokenizer.Position = pos;
            }
        }

        /// <summary>
        /// Async version of Execute
        /// </summary>
        /// <returns>The number of statements executed as part of the script inside.</returns>
        public Task<int> ExecuteAsync()
        {
            return ExecuteAsync(CancellationToken.None);
        }

        public Task<int> ExecuteAsync(CancellationToken cancellationToken)
        {
            var result = new TaskCompletionSource<int>();
            if (cancellationToken == CancellationToken.None || !cancellationToken.IsCancellationRequested)
            {
                try
                {
                    var executeResult = Execute();
                    result.SetResult(executeResult);
                }
                catch (Exception ex)
                {
                    result.SetException(ex);
                }
            }
            else
            {
                result.SetCanceled();
            }
            return result.Task;
        }

    }

    /// <summary>
    /// 
    /// </summary>
    public delegate void MySqlStatementExecutedEventHandler(object sender, MySqlScriptEventArgs args);
    /// <summary>
    /// 
    /// </summary>
    public delegate void MySqlScriptErrorEventHandler(object sender, MySqlScriptErrorEventArgs args);

    /// <summary>
    /// 
    /// </summary>
    public class MySqlScriptEventArgs : EventArgs
    {
        private ScriptStatement statement;

        internal ScriptStatement Statement
        {
            set { this.statement = value; }
        }

        /// <summary>
        /// Gets the statement text.
        /// </summary>
        /// <value>The statement text.</value>
        public string StatementText
        {
            get { return statement.text; }
        }

        /// <summary>
        /// Gets the line.
        /// </summary>
        /// <value>The line.</value>
        public int Line
        {
            get { return statement.line; }
        }

        /// <summary>
        /// Gets the position.
        /// </summary>
        /// <value>The position.</value>
        public int Position
        {
            get { return statement.position; }
        }
    }

    /// <summary>
    /// 
    /// </summary>
    public class MySqlScriptErrorEventArgs : MySqlScriptEventArgs
    {
        private Exception exception;
        private bool ignore;

        /// <summary>
        /// Initializes a new instance of the <see cref="MySqlScriptErrorEventArgs"/> class.
        /// </summary>
        /// <param name="exception">The exception.</param>
        public MySqlScriptErrorEventArgs(Exception exception)
          : base()
        {
            this.exception = exception;
        }

        /// <summary>
        /// Gets the exception.
        /// </summary>
        /// <value>The exception.</value>
        public Exception Exception
        {
            get { return exception; }
        }

        /// <summary>
        /// Gets or sets a value indicating whether this <see cref="MySqlScriptErrorEventArgs"/> is ignore.
        /// </summary>
        /// <value><c>true</c> if ignore; otherwise, <c>false</c>.</value>
        public bool Ignore
        {
            get { return ignore; }
            set { ignore = value; }
        }
    }

    struct ScriptStatement
    {
        public string text;
        public int line;
        public int position;
    }
}